Some Basic Weed Warnings

The San Francisco Office of the Chief Medical Examiner suggests that female heart patients, drinkers, and gang-bangers may want to lay off pot.

It's a proven fact: You can't overdose by smoking marijuana. But new research suggests that pot might be harmful for people with damaged hearts.

That's just one takeaway from a slew of studies released by the San Francisco Office of the Chief Medical Examiner. In addition, a review of recent forensic toxicology conference proceedings and an interview with Nikolas Lemos, chief forensic toxicologist and lab director in San Francisco, suggest that marijuana will one day come with basic warning labels like: "People with heart problems should check with their doctor before using pot"; "don't combine with alcohol"; and "may cause drowsiness and impair judgment."

Heart Conditions

This issue is chief among Lemos' concerns. For the last decade, the San Francisco Office of the Chief Medical Examiner has been doing some relatively rare research: looking for weed in the blood and urine of people who've died, which is not part of routine protocols. A review of 1,338 cases over a one-year period found that 8 percent of the people who died and were examined by the medical examiner's office tested positive for cannabis.

Studying this population also revealed a possible association between cannabis use and a larger heart size — regardless of the person's Body Mass Index. The average human heart weighs up to 350 grams, but for those who died of natural causes and had cannabis in their blood, their heart weighed 520 grams on average. For women in that category, the average weight shot up to 676 grams. "That's a very profound cardiomegaly [enlarged heart]," said Lemos.

Cannabis can be hard on the heart, Lemos said. Patients sometimes report a racing pulse, and pot can increase blood pressure and body temperature. In the 2013 proceedings of the International Association of Forensic Toxicologists in Portugal this September, Lemos wrote that his new pot tests "permitted the pathologist to evaluate the role cannabis may have played in death. Cannabis has routinely been included as either contributing to the 'cause of death' or as a 'significant other condition' on death certificates especially when significant cardiac pathology such as hypertensive heart disease, atherosclerotic cardiovascular disease, and cardiomegaly was also present. In some cases the pathologist reached the opinion that the decedent had suffered probable lethal cardiac arrhythmia."

Just like with sex or hiking, people with heart problems might want to ask their doctor before they initiate marijuana use. "We feel that people with cardiopathologies, any heart problems, they need to start thinking, 'Should I be using this drug or not?'" Lemos told us.

Don't Mix with Alcohol

The Office of the Medical Examiner also deals with the aftermath of San Francisco's vehicular collisions and Lemos emphasized that cannabis should not be combined with alcohol, as the two substances multiply each other's effects.

National Highway Traffic Safety Association research in The Netherlands showed that people with a blood alcohol content of 0.04 percent acted like they had 0.09 percent when given a low dose of cannabis. A high dose of pot turned drivers with 0.04 percent blood alcohol into the sloshed equivalent of someone with a 0.14.

According to proceedings from the American Academy of Forensic Sciences in February, Lemos found that 12.3 percent of the 919 driving-under-the-influence cases in San Francisco from 2010 to 2011 involved marijuana. Those drivers averaged 29.7 years of age, and 88 percent of them were male.

Most of these drivers had also been drinking, and blood tests revealed an average 0.13 percent blood alcohol — well over the legal limit of 0.08 in California. But the drivers had also been recently smoking pot, averaging 5 nanograms per milliliter of THC. A minority of the cases for which blood was available (29 out of 108) showed that cannabis was the sole drug present.

Pot contains a less popular but more therapeutic molecule called cannabidiol that has come into vogue in the Bay Area. It's also showing up in DUI deaths now, said Lemos. "CBD has a lot of sedative properties," he said, adding that it can increase the likelihood of a crash.

May Impair Judgment

Cannabidiol is also showing up in date-rape toxicology, Lemos tells us. While alcohol remains the number-one date rape drug by far in America, alcohol plus marijuana is common as well in sexual assault cases.

In the same American Academy of Forensic Sciences proceedings this February, Lemos looked at 150 cases of drug-facilitated sexual assault between 2010 and 2011. In 101 cases, only urine samples were available from the victims. Of those, 33 cases found no drugs, 28 were positive for alcohol, 33 for cocaine, and 14 showed the marijuana metabolite THC-COOH. In 2013, "we see a lot of drug-facilitated sexual assault cases with CBD only," Lemos added.

Lastly, the medical examiner is seeing some pretty high levels of THC in homicide victims with pot in their systems. While the average age of a person who died a natural death with pot in their system was 40, homicide victims with cannabis in their blood averaged 29 years of age. Homicide victims on pot averaged three times as much THC in their blood as the rest of those who died with cannabis in their blood. "They die with very high amounts of THC in their bloodstream while still under heavy influence of THC," Lemos said. "The question is, did they not realize 'This is life and death'? Were they so stoned?"

Correlation or causation? More research needs to be done, Lemos said.

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